The present invention relates to a head gimbal assembly (HGA) with a precise positioning actuator for a head element such as a thin-film magnetic head element or an optical head element.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
Recently, recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by a voice coil motor (VCM) only has never presented enough accuracy.
In order to solve this problem, an additional actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCM only. The techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese patent publication No. 08180623 A.
As for a precise positioning actuator, there are various structures of actuator such as for example a load-beam structure actuator and a piggy-back structure actuator.
The load-beam structure actuator has two piezoelectric elements of PZT attached on a load beam of a suspension. These PZT elements are driven in a manner to support with each other to displace the load beam so as to perform fine precise positioning of a magnetic head slider mounted on the load beam.
The piggy-back structure actuator is formed by piezoelectric material of PZT in an I-character shape with one end section to be fixed to a suspension, the other end section to be fixed to a magnetic head slider and a pillar shaped movable arm connected between these end sections. The PZT is driven to perform fine precise positioning of the magnetic head slider directly attached to this actuator. On the suspension, stepwise stacked are the actuator and the magnetic head slider, namely, the actuator is caught between the suspension and the slider to form a stacked cantilever structure.
However, the aforementioned conventional precise positioning actuators had following various problems:
(1) Mechanical resonance was occurred at a relatively low frequency;
(2) Since the actuator as a whole consists of piezoelectric material such as PZT of a brittle material, shock resistance is very poor. Particularly, since in case of a piggy-back structure actuator, the actuator and the magnetic head slider are stacked to form a cantilever structure, a shock easily occurs with a moment and also shock resistance is extremely poor;
(3) Depending upon the size of the magnetic head slider, a travel of the magnetic head element during the precise positioning operation varies. Thus, it is difficult to obtain enough stroke;
(4) Handling at the time of an assembly of the HGA is very difficult;
(5) Particularly, in case of a piggy-back structure actuator, because of the stepwise stacked structure, a total thickness of the HGA around the magnetic head slider increases by the thickness of the actuator;
(6) In case of a piggy-back structure actuator, because of three-dimensional and complicated attachment structure, the handling at the time of an assembly of the HGA is extremely difficult and it is impossible to use a conventional HGA assembly equipment causing productivity to be very worse; and
(7) In order not to interfere with the movement of the piggy-back structure actuator, it is necessary to assemble with keeping a gap between the actuator and the magnetic head slider and also between the actuator and the suspension. However, forming of such gaps will more decrease the shock resistance and it is difficult to precisely keep the gaps constant. Particularly, since it is difficult to keep the suspension, the actuator and the magnetic head slider in parallel precisely, the head characteristics deteriorates.
To solve the aforementioned various problems, the inventors of this application had proposed an actuator provided with a pair of metal plate movable arms for fixing and catching a magnetic head slider in a space between the movable arms (Japanese Patent Application No. 2000-332255).
The present invention intends to provide an HGA using a metal actuator, which can be more easily fabricated. In other words, it is an object of the present invention to provide an HGA with a precise positioning actuator for a head element, whereby a manufacturing process of the HGA can be simplified.
According to the present invention, an HGA includes a head slider provided with at least one head element, a precise positioning actuator fixed to the head slider for precisely positioning the at least one head element, a flexure made of a metal plate member for supporting the actuator and a load beam fixed to and for supporting the flexure. The actuator includes a pair of movable arms each formed by a metal plate that is substantially in parallel with a side surface of the head slider. Top end sections of the pair of movable arms are capable of displacing in response to a drive signal applied to the actuator along a direction crossing planes of the metal plate. The flexure and the actuator are unitarily formed.
The frame of the actuator, made from a metal member and the flexure made from a metal member are unitarily formed by a metal plate. Therefore, no process for partially fixing the actuator to the tongue of the flexure is necessary resulting a manufacturing process of an HGA can be simplified. It should be noted that, according to the present invention, the actuator itself shares the function of the tongue of the flexure.
It is preferred that the actuator further includes a coupling section connected between the top end sections of the pair of movable arms and formed by a metal plate that is substantially in parallel with a one surface of the head slider, which one surface is opposite to an air bearing surface (ABS) of the head slider and fixed to the coupling section. Since the actuator is provided with a coupling section connected between the top end sections of the pair of movable arms and the head slider is to be fixed to this coupling section, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
Further, the movable arms and the coupling section are mainly made from a metal plate, the weight of the whole actuator can be reduced and thus a mechanical resonance frequency of the actuator can be increased. Also, as a basic member of the arms is formed by the metal plate that is strong and light-weighted, a shock resistance of the movable arms that are particularly weaken for the shock can be greatly improved. Due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. By using the metal plate to form the main portion of the actuator, the flexibility on a design of the actuator will improve with the shape and/or size. Thus, it is enabled to design the actuator with a sufficient stroke. Furthermore, because the metal plate can be precisely machined, accuracy in size of the actuator itself can be greatly improved.
Also, since the head slider will be mounted in a space between the movable arms, the thickness of the HGA around the head slider does not increase even if the actuator is attached. Thus, no modifications in size of the disk drive apparatus due to the mounting of the actuator is necessary. In addition, since the head slider is caught in between the movable arms, the top end sections of the movable arms, which actually transfer the displacement to the slider, can be extended to always position at the top end of the slider. Thus, it is possible to provide a constant travel to the slider even if the size of the head slider changes, and therefore an enough stroke of the head at the precise positioning operation can be always obtained.
Because of a partial fixing of the head slider to the coupling section of the actuator, shape change in the ABS of the head slider (generation of crown or camber) can be prevented from occurring even if the adhesive deforms due to change in atmosphere temperature.
It is also preferred that the actuator further includes a base section formed by a metal plate that is in parallel with the coupling section, and that the pair of movable arms extend forward from the base section. As not only the movable arms and the coupling section but also the base section are made from a metal plate, the weight can be more reduced and a shock resistance can be more improved. Also, accuracy in size of the actuator itself can be greatly improved.
It is preferred that the base section of the actuator includes a strip and a projection protruded forward from the strip, a load being applied to the projection from the load beam. In this case, preferably, the projection has side edges each having an arc shaped section.
Since the actuator shares the function of the tongue of the flexure, in operation, a load is applied to the actuator from a dimple of the load beam. According to the invention, this load is received by the projection protruded forward from the base section. However, since the actuator and the flexure are unitarily formed, it is impossible to thicken the projection only. Therefore, to increase the rigidity of the projection, the frame of the actuator is roundly bent so that each of the side edges of the projection has an arc shaped section. As a result, the projection will hardly bend even if the load is applied from the load beam.
It is further preferred that the pair of movable arms, the coupling section, the base section and the projection of the actuator have a U-shaped section structure formed by bending a single metal plate. Since the main portion of the actuator is configured by bending a single metal plate, its fabrication becomes easy and a mechanically strong actuator can be provided.
It is preferred that each of the pair of movable arms consists of an arm member made of the metal plate, and a piezoelectric element formed or adhered on a side surface of the arm member. In this case, the piezoelectric element has a multi-layered structure or a single layer structure of a piezoelectric material layer and of an electrode layer. If the piezoelectric element is formed in the multi-layered structure, sufficient displacement will be obtained at low drive voltage and a horizontal shock resistance will be increased.
It is preferred that the metal plate is a stainless steel plate.
It is preferred that the at least one head element is at least one thin-film magnetic head element.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.